Abstract: The multiple steady state features for the simultaneous oxidations of ethylene and carbon monoxide on platinum foil are investigated by experiments.The experimental results illustrate that the maximum number of the stable steady states is two for the specific system. With increasing the concentration of ethylene and ／or carbon monoxide,the ignition temperature increases,but the extinction temperature decreases,the region of operating arameters in which multiple steady states exist enlarges.When the concentration of carbon monoxide or ethylene is higher than some critical value,the reaction System will appear self-sustained,and extinction can not be observed during the experiments.From the analysis on the multiplicity features of the simultaneous oxidations,we know that the multiple steady state features of this system are different from separate ethylene oxidation or carbon monoxide oxidation on the same catalyst．From the multiplicity features of the simultaneous oxidation system the mechanism is found to be parallel reaction,but not consecutive reaction.In addition to thermal interaction,there exists kinetic inhibition between the two reactions.